COLUMBIA GLACIER 75 



of the antecedent condition of the glacier. On the one 

 hand, the embayment may have been so full of ice that the 

 surface gradient was outward; or, on the other, the glacier 

 of the main valley may have had so low a surface that 

 there was no tendency to overflow to the comparatively 

 shallow side valley. 



The first case implies snow accumulation in the embay- 

 ment a few decades ago at a rate not since maintained, 

 and would correspond to a general expansion of glaciers 

 followed in later decades by contraction; but the rela- 

 tions of the ice to the forest, to be described presently, 

 show that such contraction has not taken place. The 

 second case implies a general expansion of the glacier as 

 the important element of its later history. 



Another medial moraine of the great ice field north 

 of the nunatak passed just east of the nunatak and 

 continued down the eastern arm of the glacier to its 

 end, where it contributed toward the building of a 

 great alluvial delta which was gradually obliterating one 

 of the lakes. 



At the western margin of its principal tidal cliff the 

 glacier rested on a bank of drift at the level of low tide, 

 and this bank extended eastward as a shoal, on which 

 bergs were stranded, for several hundred yards from the 

 shore. A bank also extended eastward from the island 

 against which the ice front rested, constituting at low 

 water a stony cape half a mile long near the foot of the 

 ice cliff. These banks testify to a lingering, or linger- 

 ings, of the ice front near the position of its modern maxi- 

 mum, but it is not easy to estimate the duration of the 

 lingering. The western bank is built in deep water, 

 but may have been constructed rapidly, as the contig- 

 uous portion of the glacier is heavily charged with drift. 

 The eastern bank margins a part of the glacier front 

 carrying little debris, but occupies an arm of the bay which 



